Fluid drive tractor



May 25, 1965 M. F. JACKSON FLUID DRIVE TRACTOR 8 Sheets-Sheet l Original Filed Feb. 14, 1952 May 25, 1965 M. F. JACKSON FLUID DRIVE TRACTOR 8 Sheets-Sheet 2 Original Filed Feb. 14, 1952 INVENTOR.

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May 25, 1965 M. F. JACKSON FLUID DRIVE TRACTOR 8 Sheets-Sheet 7 Original Filed Feb. 14, 1952 8 Sheets-Sheet 8 Original Filed Feb. 14. 1952 United States Patent() 3,185,241 FLUiD DRIVE TRACTR Mcirin 1F. Jackson, Racine, -Wis., assigner to '.I. I. Case Company, Racine, Wis., a corporation of Wisconsin @riginal applieationheh. 14, 1952, Ser. No. 271,493, now

Patent No. 2,791,234, dated May '7, 1957. 'Divided and this application Dec. 6, 195i), Ser..No. 84,471

9 Claims. (Cl. 1563-53) The present invention relates to tractors and particularly to the power transmission mechanism thereof, and is a division of application Serial No. 271,493, filed February 14, 1952, now Patent No. 2,791,284, and an object of the invention is to generally improve theconstruction and operation of devices of this class.

Tractors are slow speed vehicles in which the necessary draw-bar pull is developed by an extreme reduction in revolutions per minute between the propellingengine and the traction wheels,.a typical example calling for a speed of 1200 r.p.m. at the crankshaft of the engineand a speed of 26 r.p.rn. at the -rear axle or traction wheels. However, at times when the maximum draw-bar pull is not required, it is not necessary to run the engine at such a high rate, and a diiierent rate of reduction is used, the

engine being throttled or slowed down to obtainthe de-V sired rate of travel, which would otherwise be too-fast. Three or four rates are commonly provided by means of a shiitable gear set, but often the most desirable ratio lies between two of ithose available and as a result it is necessary to use the next higher .ratio orenginespeed to the ideal, resulting in less than the highest possible eihciency. It is a major object ofthe invention to provide a transmission for such a vehicle which will give a multitude of ratios or a substantially inlinitely variable ratio betwdeen the engine and the traction wheels.

A further object is to provide such a device which will eliminate a large number of parts common tothe conventional transmission, and vwhich in itself is made up of relatively few simple and inexpensive parts, not subject to excessive wear, orliable to failure.

A further Objectis to provide such a device `which operates by means offluid pressure, andto improve the units acting with the iiuid pressure so as to reduce friction, in efficiency and wear to the lowest possible amount.

In tractors it is commonly necessary to have a diierential drive between the traction wheels, out at rtimesitis essential to provide for individual control of said wheels, as for example when making sharp turns, in which event one traction wheel is bralted or retarded to assist in forcing the tractor to turn. Such tractors commonly have two traction wheels and the invention will be illustrated by means of such a tractor, but it is'to be understood that the principles involved are equally applicable to tractors having more than two traction wheels, and it is not intended to limit the'invention to tractorshaving two traction wheels, such a structure beingchosen merely for convenience and as typical. Furthermore, it is often desirable to avoid differential driving of the wheels when one wheel is on a slippery spot and-spins'freely and ,diiierential driving would prevent transmission of any eiective torque to the other.

it is a further object ofthe invention to provide forindependent driving of the'traction wheels without a diiierential eilect when desired, to provide for dividing the power between the traction wheels in any desired ratio, to provide a braking effect on eitheror both wheels, and to provide simple and easily managed controls for such a transmission.

A further object is to provide advantageous means for actuating such controls and tor maintaining the requisite volume of iiuid in the system, including expedientsior ice collecting `unavoidable leakage and returning -it -to the system. i

A further object is to providey an improved arrangement of power take-cti which will be capable `of operation `at a substantially constant rate independently of vdesired variations in forward travel of the tractor.

A further object is toprovide for a belt pulley which is capable of `operation at a-substantially constant rate independently of desired variations in Vforward travel of -the tractor.

A further object is to provide for operation of a-belt pulley while avoiding constant idleroperation of any substantial portion of the traction mechanism.

Another Objectis to provide the-mechanisms and expedients necessary for the realization of the above objects.

Further objects and advantages will be apparent from the following specification vand accompanying drawings in whichasatisfactory embodiment is shown,but it is to be understood that the drawings and description are intended to be exemplary rather than restrictive.

In the drawings, FIGURE l is a vertical longitudinal sectional View with parts not relating to the invention removed and others broken away, of a tractor built in vaccordance with the invention;

FIG. 2 is a plan view of the same partly in horizontal section;

FIG. 3 is a vertical transverse sectional view on the line 3 3 of FIG. l;

FIG. 4 is a sectional View of the parts shown in FIG. 3, taken on the line 4-4 O'FIG. 3;

FIG. 5 is a horizontal sectional view taken on the line 5-5 of FIG. 4, with the parts in a slightly different position;

FIG. 6 is a rear elevation of a cover plate or head indicated in FIG. 4;

FIG. 7 is an elevation of the same part ltakenfrom the iront orface as for example onthe line 7 7 of FIG. 4 with parts removed;

FIG. 8 is anenlarged vertical transverse sectional view imilar to FIG. 3 with parts removed, italien on the line S-S of FIG. l showing a neutral position;

FIG. 9 is a similar view of the same parts in an operating position;

FIG. l() is an exploded View, Alooking backwardly, downwardly and from the rightrof certain pants indicated in FIGS. l and 2;

FiG. 11 is a sectional view takenron the line 11--11 of FIG. l;

FIG. 12 is a sectional View of the structure of FIG. 10 on the line 12-12 of FIG. l;

FIG. 13 is a sectional view on the Aline 13-13 of FIG. l;

FIG. 14 is a sectional development taken Von the line 16e-14 of FIG. 10;

FIG. l5 is a sectional development on the lines 15-'15 of FIG. 10, there being two separate portions ofthe part shown in FIG. l0 which are conveniently-made identical and represented by FIG. 15;

FIG. 16 is a sectional development taken on vthe line 1S-16 of FIG. 10;

FIG. 17 is a vertical sectional view taken on the line 1'7-17 of FIG. 13;

FIG. 18 is a vertical sectional View taken on the line 18-18 or" FIG. 1;

FIG. 19 is an enlarged sectional viewof an auxiliary pump #taken on the line I9-19 of FIG. l;

FIG. 20 is a vertical section of the same on the line 26-219 of FIG. 19;

FIG. 2l is a diagrammatic representationof the units of the variable speed transmission'of the tractor showing particularly the iiuid circuits;

FIG.V 22 is a similar view of certain parts indicated in FIG. 2l shifted to a different position;

FIG. 23 is a similar view showing the parts in another position;

FIG. 24 is a similar view showing the parts in still another position;

FIG. 25 is a plan View of a modified tractor construction embodying the invention;

FIG. 26 is a vertical sectional view on the line 26-26 of FIG. 25;

FIG. 27 is a rear elevation of the embodiment shown in FIG. 25 with parts broken away and others omitted, to avoid confusion;

FIG. 28 is a vertical sectional View on the line 28-28 of FIG. 25;

FIG. 29 is an enlarged perspective View of a vane indicated in FIGS. 1, 3, 8 and 9;

FIG. 30 is an end elevation of the same partly broken away;

FIG. 31 is an enlarged perspective view of complementary block portions which are adapted to be assembled to form a vane indicated in FIGS. 1, 2 and 11;

FIG. 32 is a front elevation with parts broken away of an assembled vane such as indicated in FIG. 31; and

FIG. 33 is an end View of the same partly broken away.

General description Referring to FIGS. 1 and 2 the tractor illustrative of this invention has an engine generally designated as E, a clutch C, a transmission T, traction wheels Wl and W2, a power take-oli" shaft P, and a belt pulley B. Wheels W1 and W2 are carried by axle housings A1 and A2 in well-known manner not necessary to further describe, and housings A1 and A2 are connected to engine E by means of a housing H which encloses most of the parts of the transmission mechanism T and unites the whole into a unitary assembly as is common in tractors generally.

Certain features which are conventional and well-known to al1 tractors, such for example as the front wheels, steering gear, details of the engine, etc., all of which may be of any Well-known type insofar as the invention is concerned, have been omitted for the sake of simplicity.

In the present instance, engine E drives, through above mentioned clutch C a clutch shaft connection or motion transmitting means 50 which as will be more fully described actuates a duplex hydraulic pump generally designated as 52. Pump 52 supplies fluid pressure through conduits 54 and 56 to a control valve generally designated as 58 which distributes the pressure iiuid to a duplex fluid motor generally designated as 60.

For the best understanding of the invention, reference is also made to FIG. 21. Clutch shaft 50 drives, through intermediate mechanism which willbe described presently, a main input shaft 62 of above mentioned pump 52 on which are mounted rotors 64 and 66 rotatable within stators 68 and 70 respectively. Rotor 64 and stator 68 are received yin iiuid tight relation between head 72 and a dividing wall 74, while rotor 66 and stator 7i) are also received in fluid tight relation between above mentioned dividing wall 74 and a rear head 76. Rotor 64 and stator 68 cooperate in a manner which will be further described to force pressure .fluid from a supply pipe or manifold 78 to above mentioned pipe or conduit 56, while rotor 66 and stator 70 cooperate to force pressure fluid from above mentioned manifold '78 into above mentioned pipe or conduit 54, the two streams of fluid in pipes 54 and 56 enter valve 58 whence they are distributed in one or another of various ways, as will be further described, betweenA passageways 80 and 82 (see also Fig. 1l) leading respectively to a cooperating rotor 84 and stator 86, and to a cooperating rotor 88 and stator 90, rotors 84 and 88 being individual to and connected in driving relation with Wheels W1 and W2 respectively. Spent pressure fluid from stators 86 and 90 finds its way to branches 92 and 94 of manifold 78, and returns to pump stators 68 and 76, the

flow of iiuid in this manner causing rotation of rotors 84 and 88 and driving of traction wheels Wl and W2.

The iiuid delivered by rotors 64 and 66 of duplex pump 52 may be precisely regulated in volume in a manner t0 be described and, as will be apparent, the ratio of revolutions of the pump to revolutions of the motor rotors is accurately controlled. The fluid from both pump rotors 64 and 66 may be intermingled in valve 58, in which case it will divide between rotors 84 and 88 in accordance with the speeds thereof for a differential driving effect, or if desired the two streams may be kept separated in valve 58, all as will be described in detail, so that the iuid will be divided between the rotors 84, and 88 substantially equally even in the event that one rotor is without substantial resistance to rotation. This condition might arise for example if one traction wheel were free to slip, in which condition the conventional tractor would be helpless even though the other Wheel had satisfactory traction.

Additional control may be obtained through valve 58, which may be manipulated to block,l or partially block the ow of pressure iiuid through one or the other of stators 86 or 90 which will introduce a braking effect on the corresponding traction wheel so as to assist in certain maneuvers, such as turning sharply to the right or left.

It is a feature of the device disclosed that the tractor equipped with it operates with about equal facility either forward or backward. This is particulariy convenient in the use of certain attached implements which require the tractor to run backward when the implement is operating. With a conventional tractor it is necessary to reverse the position of the usual driven bevel gear in order to obtain even the usual variety of speed ratios in this reverse direction. With the present transmission substantially continuous variation of the speed ratio is equally available in either direction of operation.

Detailed description Returning to a more complete description of the illustrative mechanism, engine E is of well-known type including the usual crank case 96, cylinder block 9S, crank shaft 100, and flywheel 102, the latter carrying a starter gear 104 of suitable type. Flywheel 102 includes within itself most of the working parts of clutch C which may be of any type suitable or usual for use on tractors within the contemplation ofthe invention, and which therefore need not be further described except to say that it has a housing portion 106, and may be thrown into and out of engagement by means of a rock shaft 108 journaled in housing H and rockable by means of a control 110, FIG. 2. Rock shaft 198 has shipper forks 112 and 114 which engage and shift a throwout bearing 116, connected in Well-known manner with the mechanism within iiywheel 102 and housing 106 so that rocking of rock shaft 188 by means of control 119 will canse establishment or interruption,

Vas desired, of driving relation between crank shaft 18) and above mentioned clutch shaft 50.

Shaft 50 extends rearwardly through a suitable bearing 118 and has slidably keyed thereon a spiral or other suitable gear 120 engaged with a cooperating gear 122 fixed in relation to a shaft 124 carrying above mentioned belt -pulley B, shaft 124 being carried in suitable bearings 126 and 128 supported in the Walls of housing H. Gear 120 may be shifted axially of shaft 5t) by means of a shifter fork 130 engaged in a groove 132 and fixed in relation to a shifter rod 134 slidable in bosses 136 and 138 supported in housing H. Rod 134 has a handle portion 140 by means of which it can be readily reciprocated with the result of shifting gear 120 into and out of mesh with gear 122. In this way belt pulley B may be caused to run whenever clutch C is engaged, or may be disconnected from clutch C as desired.

Shaft 50 has a pilot bearing 142 in above mentioned input shaft 62, and a collar or clutch element 144 is slidably keyed on shaft 50 and shiftable into slidab-le but non-rotative engagement with shaft 62 so as to connect shafts 50 and 62 or to disconnect them when desired. A `shifter fork 146 engages a groove .148 in collar v144i, and is xed in relation to a rod l151i slidable in a manner similar to above mentioned rod 134, and having a handle portion 152 by means of which, though fork 146, collar 144 may be shifted. Itis therefore possible to avoid continuous operation of pump :52 when it is not needed, as, for example, when the tractor is to be used in a stationary position for actuating an implement by means of belt pulley B.

Power take-off Shaft 62 continues rearwardly through pump 52 and beyond the latter has a gear 154 xed thereon and meshing with a gear 156 slidably keyed on a shaft 158 constituting above 4mentioned power takeoff P. Gear 156 has a grooved hub portion 161i engaged by a shifter fork 162 carried on a rod 164 slidable in a bracket 166 and a wall portion 168 of housing H. Rod 164 has a handle portion .171B by which it may be shifted axially, thus moving shifter 162 and shifting Vgear 156 into or out of engagement with gear 154. Power take oit shaft P may accordingly be caused to run whenever pump input shaft 62 is actuated and regardless of the adjustment of pump 52 and accordingly of the rate of progress of the tractor. Power take-off P is accordingly independent of the forward motion and may continue to run at a steady rate while the movement of the tractor is varied or discontinued altogether, this resulting in substantial advantages under certain types of operation of the tractor. For example in actuating a harvesting machine which has mechanism which must be operated at a -steady speed but where the rate of progress .governs the intake of material, engine E and power take-oit P may run at a governed speed (which is customary) while the forward progress may be completely controlled from maximum to stand-still by adjustment of pump 52. Suitable or well-known detent means 171 is contemplated for maintaining shifter rod 164 in adjusted positions and means is contemplated in connection with shifter rods 134i and `159.

Pumps and adjustments Referring to FIGS. 1, 8 and 9, the pump is in reality a duplex unit having two pumping chambers in a single casing. Above mentioned rotor 66, FIG. 9, is preferably identical with rotor 64, FIG. 1, and the principle of operation of the two is the same so that it will benecessary to describe in detail only one. As seen in FIG. 9, rotor 66 is disposed accurately on the axis of an outer or housing ring 173 and remains concentric therewith at al1 times. Within ring 173, however, is above mentioned stator 70 which constitutes a shiftable casing for rotor unit 66. As seen in FiG. 9, stator 70, which is journaled on a pivot 174, has been shifted upwardly a maximum possible amount so that rotor 66is in effect downwardly displaced or eccentric to t stator 70. A plurality of vanes or abutments 176-176 extend outwardly from rotor 66 into contact with the inner surface of stator 70, which surface is suitably iinished for continuous sliding contact of said vanes. As rotor 66 rotates, the spaces between vanes 176 expand and contract, in FIG. 9 drawing fluid in between them through a circumferentially extending slot or port 17S in head 76 and expelling it through a similar port 130 communicating directly with above-mentioned conduit 54.

Varies 176 as more particularly shown in FIGS. 29 and 3() are formed of materials suitable for running in Vfrictional contact with a surface 182 of stator 70, various metals being suitable and hard wood having been found to operate satisfactorily. Each vane has a rectangular or wafer-like contour and is tapered at one edge as at 184 to a narrow contacting surface 136. At the end remote from 134 the tapered-surface is cut away as at 13S. The vanes are made both as shown in FIG. 29 and in the reverse, or with cut-away portion 188 at the opposite end, vanes of the type shown in FiG. 29 being used with .or another of the vanesin contact with port 2.66.

rotor 64 and the opposite type with rotor 66. The cutaway portion 188 of each vane is directed toward the ports 17S and 180 co-acting with rotor 66 and with similar ports 196 and 192, FIG. 5, cooperating with rotor 64. Varies 176 are also provided with recesses 194-194 within which springs 196-196, FIG. 9, rare compressed to continuously maintain vanes 176 outwardly against surface 132. Cut-away portions 1SS provide for the utmost possible freedom of entrance and exit of iiuid between ports 178 and 180 and the spaces between vanes 17 6-176- The volume of uid pumped by the arrangement is proportional to the degree of offset or eccentricity between rotor 66 and stator 70 and this may be adjusted by means of a stem 198 slidable-in a portion 206 of housing 173 and connected with stator 70 by suitable means such as a pin and slot connection 202. Vertical movement of stem 198 will cause pumping, as in FIG. 9, assuming clockwise rotation ofrotor 66 as indicated by the arroWl-f-t, from port 178 to port 18?. Downward movement of stem 198 to the FIG. 8 position will result in a cessation of any pumping and furthermore, assuming substantially incompressible uid, such for example as oil, while rotor 66 mayfcontinue to run, flow of uid from port 17S to port V186 is Vvirtually blocked or prevented since there is no expansion or contraction of the spaces between vanes 176 under this condition. It will be apparent that further downward movement of stem 193 will result in eccentricity between rotor 66 and stator 75) in the opposite direction from that shown in FiG. 9. The expanding spaces between vanes 176 will then be in communication with port while the contracting spaces will be in communicationwith port 17S. As a result fluid will then be pumped from port V13) to port 178, reverse rotation thus being brought about in kany fluid motor or motors connected with this section ofthe pump at the time.

As stated rotor 64 rotates within casing'68 in a manner substantially identical to that just described, the only difference being that the ports 173 and V18() cooperating with rotor 66 are at the left as seen in FIG. 1 while the corresponding ports and 192 cooperating with rotor 64 are at the right as seen in FIG. l.

Ports 173 and 139 as best shown in FIG. v7 -are separated by plane surfaces 266 and 298 which separate the circumferential ends of the ports. These surfaces are continuous with the face of'head 76 against .which stator 70, rotor 66 and the ends of vanes 176 are slidable in substantially fluid tight relation. In operation, as will be understood, working pressure or high pressure will be present in one of theports, for example port 134i, while comparatively low pressure will be present in port -178 under these conidtions. Fluid has free access Vto both sides of all vanes communicating with port '182i as seen in FIG. 9 and the pressure will be equal on all sides thereof with the exception of whichever vane as 21'. happens at the instant to be in contact with surface 286.

This vane will have high pressure on one side and low pressure on the other. This situation changes as other vanes come into this position, the force being Vtransferred from one to the next as rapidly as the vanes pass beyond Asurface 266 into .juxtaposition with port 189. The high pressure is excluded from port V178 accordingly by one 1n the position shown in FiG. 9, rotor 66 seals the highpressure from port .178 by directcontact with surface 182 in the region of surface 23S. In other settings ofthe partsone or another of vanes 176 seals the pressure against escape into port 173 through cooperation with surface ,293 in a manner similar to that just described in connection with surface 266. As will be apparent, one side, so to speak, of rotor 66 is subjected to very substantial iluid pressure while the other side is not. As a result there is a strong tendency for the rotor to be displaced (toward the left in FlG. 9) and which pressure must be resisted in some As has been pointed out, rotors 66 and 64 are identical and close to each other on shaft 62. The connections with motrv69, as will be fully described, are such that, in order to obtain the desired direction of rotation, stator 70 is displaced in one direction, for example upwardly, resulting in a side thrust of rotor 66 toward the left as seen in FIG. 9, while stator 68 is displaced downwardly, resulting in a side thrust to the right, considered from the same viewpoint as FIG. 9. We thus have reactions against rotors 66 and 64 which are substantially equal and substantially in opposite directions thus relieving the supporting parts of a very considerable amount of stress which otherwise would be imposed thereon. Above mentioned shaft 62 is carried in very rugged bearings 212 and 214 mounted respectively in heads 72 and 76 but, as stated, these bearings are relieved from most of the side thrust caused by the fluid pressure on the sides of the pump rotors, since one rotor balances the other, any slight remaining unbalanced force vbeing resisted by bearings 212 and 214. Any such force is very small compared to what it would be if the entire reaction were exerted in one direction.

In carrying out this action, mechanism is provided for displacing stators 68 and 7in opposite directions. Referring to FIGS. 3, 4 and 5, above mentioned stern 198 has a counterpart in a stem 216 which is also connected by a pin and slot connection 218 with stator 68. Stem 198 has a cylindrical rack element 220 comprising a series of equally spaced disk-like collars 221--221, engaged with a gear 222 as more particularly shown in FIG. 2, rotatable about a shaft 224 in response to rocking of a lever 226. Forward rocking of lever 226 will accordingly cause raising of rack 226 and stem 19S while rearward rocking will cause lowering of stem 198as will be apparent. Gear 222 also engages a cylindrical rack 228 of similar or identical type fixed on stem 216. As will be apparent, movement in one direction will be accomplished by equivalent movement of the other stem but in the opposite direction. Racks 22%) and 228 form a convenient means of obtaining precise adjustment of the relation between the stators 68 and 70. For this purpose racks 220 and 228 are threaded respectively on stems 198 and 216, the adjustment being held by lock nuts 230 and 232. Lever 226 has a detent 234 engageable with a quadrant 236 and controlled by a linkage 238 from a handle 246 whereby lever 226 may be maintained in any desired position within the limits of its movement and readily released and shifted when desired. Virtually the entire control of the forward or backward movement of the tractor is centered in this lever. For any desired setting of lever 226, stator 70, for example may be accurately adjusted up or down by loosening lock nut 230 and adjusting rack 220. The same is true in relation to stator 68.

It will be noted that a somewhat similar displacing reaction will be exerted against the stators 68 and 7d but which reactions also balance each other, as will be described. Considering first stator 70 as seen in FIG. 9, all the'spaces between the vanes 176 to the right of a vertical plane containing the center line of shaft 62 are under comparatively high pressure, while all those at the left of such a plane are under low pressure. The resultant of all these individual areas of pressure will be a substantial urge to the right against the pin 174, but, since stator 70 has been displaced upwardly, this force will not be symmetrical with pin 174 but, in the relation shown, will be slightly above it. Thus there will arise a couple tending to further rotate stator 79 in a clock-wise direction about pin 174. Such rotation, unless stator 70 is already at the limit of its travel, will tend to throw the rotor into extreme eccentric position once it has been displaced the least bit from a central or neutral position such as shown in FIG. 8. On the other hand, in the case of stator 68, which, as shown in FIG. 3, is displaced downwardly under the same conditions, the spaces to the left of a vertical plane through the center line of shaft 62 will be under high pressure while those to the right of such plane will be under low pressure. This will result in a force exerted on stator 68 toward the left as seen in FIG. 3. However, in this case the force is centered in a horizontal plane slightly below pin 174, resulting in a couple tending to rotate stator 68 also in a clockwise direction, or toward a concentric or neutral position, which, it will be apparent, is the opposite of the action of stator 70, which tends to be forced to its extreme eccentric position.

This general relation will exist regardless of the direction of displacement of the stators, because of the side of shaft 62 on which the pressure is exerted. In other words, one stator will tend to go to its extreme eccentric position, while the other stator will always tend to return to a concentric position. Reference to FIG. 4 will show that movement of either statorl to either of its extreme positions, up or down, will be resisted, through racks 220 and 228 and pinion gear 222 by the tendency of the other stator to move to a central position.

A further advantage of this action is the elimination of any slack or 10st motion between the circular racks 220 and 228 and gear 222, as well as between stems 128 and 216 and their respective connections 202 and 218.

Other factors enter into the functioning of the control, for example the friction of the varies on the inner surfaces of the stators, which tends to shift both stators in an upward direction, and the pressure of springs 196 which tends to shift both stators to a central or neutral position. Another factor is the resistance to iow of luid into and out of the spaces between vanes 176, which may give rise to a pressure increase between one space and the next as the spaces -get smaller. This would also tend to shift the stators to central or neutral position.

It has been observed in practice that the factors tending to shift the stators to neutral tend to predominate so that mechanism such as detent 234 and rack 236 is necessarywto maintainthe stators in adjusted position.

Selector valve Valve 58, as more particularly shown in FIGS. 1, 10, 13, and 17, has two levels, an upper and a lower, with different porting arrangements for providing a choice of operation. It comprises a generally cylindrical plug portion 242 rotatable in a sleeve 244 and having a substantially uid tight t therein, said plug being rotated by a stem 246 journaled in cap 248, a control fitting 250 being fixed on stern 246 and a control4 bar 252, in the present instance foot operated, being xed on stem 246 above fitting 250. The upper lever of valve 58 has been generally designated as 254 while the lower lever has been designated as 256, it being understood that both portions work with the high pressure iluid as distinguished from the low pressure or spent fluid, at such times as the tractor is running in a forward direction, although, as will be presently apparent, the peculiar advantageous operation of the system is substantially the same whether valve 54. is introduced in the high or the low pressure side of the fluid circuit.

As best seen in FIGS. l, 11, 13, 17 and 2l. to 24, inclusive, upper portion 254 of valve 58 has ports 258, 260, 262 and 264, which may register simultaneously with ports 266, 26S, 276 and 272, respectively in sleeve 244, ports 58, 260, 262 and 264 intercommunicating within plug 242. Lower section 256, on the other hand is provided lwith ports 274 and 276 which constitute separate passageways through plug 242 and which do not intercommunicate. Ports 266, 268, 270 and 272 yare elongated, and of sufficient extent to register with either the upper ports 258, 260, 262 and 264, or with ports 274 and 276, and therefore may control the ow between ports 266 and 268 on the one hand, and between ports 276 and 272 on the other. Motor 60 being of the positive displacement type, it follows that various advantageous modes of operation can be obtained by shifting valve 58 to various positions.

Passageway 54 communicates with a cored extension 278, FGS. 11 and 13, which in turn communicates with port 266, while passageway -5 communicates with a cored extension 283 communicating with port 27d. Thus the streams of fluid from individual pump rotors 65 and 64 are delivered separately and independently through passageways 54 and 56 to ports 266 and 274D. Furthermore, ports 258 and 272 communicate with above mentioned passageways Sti and 82, respectively, which lead, as hereinbefore described to motor rotors he and 38. Assuming displacement of stators 7G and 63, fluid will be displaced by rotors 66 and 64, and pumped in virtually identical quantities into passageways 5d and Se, and accordingly into extensions 27h and 23u. With the valve 58 in the position shown in FIGS. 13 and 1l, which show, respectively, the upper section 254 and the lower section 256, the two streams of i-luid will be mingled in ports 258 and 252, and transmitted through ports 2d@ and 2nd to passageways 3@ and d2 and thus to rotors 34 and S8. Since the tluids are intermingled, it will be apparent that the liuid pressure applied to the two rotors will be identical, or substantially so, so that the torque developed by the iiuid motors and applied to the driving wheels or units will be the same. Since the motors are of the positive displacement type, the volume or" iiuid passing through the motors will be in accordance with the number or" revolutions of the rotors, and the fluid in valve 5S will divide between passagewa ys 8u and 32 in accordance With the rate of rotation, and therefore in accordance with the rate of acceptance of uid by the rotors 34 and 88. A differential etlect is therefore produced in which each traction unit exerts equal eort and may drive at a different rate than the other unit if the tractor is traveling in a curve, or if necessary for any other reason. It follows that, if one Wheel or unit looses traction, it will rotate freely at a rapid rate and accept all the uid supplied by both pumps while preventing the building up of any substantial pressure, since it will require very little pressure -to actuate the traction unit which has no traction. This is the hydraulic counterpart of what happens with the ordinary mechanical differential under similar circumstances.

Turning to FIG. 24, a position of valve 58 is shown which would be suitable for overcoming lthis condition, and which would be advantageous when operating under conditions where one or the other traction unit would be likely to loose traction from time to time. ln this position it will be noted that port 258 of the upper portion 254 or' the valve has been shifted until it no longer registers with port 266, the latter being blocked by the solid portion 252 of the valve between ports 25S and 262. in similar manner port 27@ is blocked by the solid portion 2de between ports 252 and 264 while ports 26S and 272 are similarly blocked by solid portions 286 and Y288 respectively. The hereinabove described differential effect is therefore prevented as in fact is all iluid dow insofar as the upper portion of the valve is concerned. Such positioning of the valve, however, also positions the lower portion 256 of the valve as also seen in FIG. 24 so that port 274 registers with ports 26d and 268, thereby connecting conduit extension 27d with passageway Sil so that the entire output (neglecting unavoidable slight leakage or slip) of pump rotor 6&3 is compelled to pass to motor rotor Sd. in similar manner port 276, in this position of the valve registers with ports 27d and 272 and thereby connects conduit extension 230 with passageway 32 so that the output of pump rotor 64 is connected exclusively with motorV rotor S3. In other respects the transmisison operates as before, but it will now be apparent that, if one traction unit is on a slippery spot so that it suiers little or no resistance to turning it will rotate freely without the development of any substantial pressure in its respective pump and motor, as before, but this will in no way affect the development of pressure by the other pump. Thus pressure will be developed in the motor connected with the traction unit which does have traction so that the tractor will be moved by the latter traction unit into a more favorable position where both units will presumably have traction.

In a word the operation will be similar to that of a locked differential, except that, because of the slight unavoidable leakage or slip a limited differential effect will be present. The tractor will therefore have the advantages of a solid rear axle when such operation is desirable, but will be more readily steered under these conditions than such a tractor.

Valve S8 may also be used as a steering or steering assisting means by diverting the pressure fluid more to one motor than to the other as will now be described. Referring to FlG. 23 it will be noted that ports 274 and 276 in the iower portion 256 of the valve lhave been shifted so that they fail to register with any of ports 266,

er?, 27@ or 272 so that iiow of uid through the lower portion of the valve is blocked. Upper portion 254 has of course also been shifted, but, unlike the condition of FiG. 24, portion 232 of the valve does not block port 265. vPortion 286 however, does block port 26S, while port 272 is left open since portion 2&8 has not been moved sufficiently to close it as was the case in PEG. 24. ln this manner, as will be apparent, all the fluid from both pump rotors 66 and 64 will be mingled and transmitted through port 272 and passagewa 82 to motor rotor 8S. In this manner all the driving force is transmitted to the traction unit connected with rotor 33.

In FIG. 22 the valve is shown shifted in the opposite direction from that indicated in FIG. 23 so that huid is transmitted through port 263 to motor rotor Sd, but in this instance the valve has not been moved so far. Portion 234 now partially, but not entirely blocks port 272 so that a tlirottling effect is produced and the fiow of iluid into passageway S2 is restricted. in this position rotor 3d will receive the full tluid pressure while a substantial pressure drop will be produced at port 272. As a result, rotor 3S will develop less torque than rotor Sli, which will tend to make the tractor turn in a direction away from the traction unit connected with rotor Se. lt will be apparent that the parts might be shifted `further to the position corresponding but opposite to that of FIG. 23, in which case port 272 would be blocked and all the uid would be transmitted to rotor S03. By throttling one or the other of ports 272 and in this manner, a steering effect can be easily produced by causing a predominance of torque or force on one or the other of the traction units. This is particularly effective when the transmission is used in a so-called crawler, as is contemplated, wh :e steering is ordinarily accomplished by distributing the driving force or power unevenly between the tracks or traction units. By merely manipulating Valve 58 the power can be directed to either motor, to both equally, or it can be divided between them in any proportion desired.

Motors Turning now to FIGS. 1, 2, l0, 11, 12, 14, 15, 16 and 2l, motor al? as above described includes rotors 84 and Sti and corresponding stators S6 and 9i?. inasmuch as the two sections of the motor are constructed and operate in a substantialiy identical manner it will be necessary to describe only one in detail. Rotor 8S is enclosed within above mentioned stator d@ and between an axle housing portion 399 and a dividing port carrying casting or unit 362, a similar axle housing Sti-fi adioining above mentioned stator de, axle housing 3th), stator 9i), dividing unit 362, stator n, and axle housing 39d, being secured rigidly together by means of suitable bolts or the like 39o- 3% to form a unitary rear axle structure for the tractor. Rotor d is splined or otherwise suitably lined at 3% to an axle shaft Si@ carried in an inboard bearing generally designated as 312, shaft Sid being xed in driving relation with above mentioned traction wheel W2 and supported in the usual outboard bearing 314. Rotation of rotor S3 accordingly causes corresponding rotation of wheel W2 and, on the other hand rotation of wheel W2 causes corresponding rotation of rotor SS with certain results which willvbe explained. Substantially identical construction is used in connection with rotor 34, a shaft 316 being carried in a bearing 31S and connected between rotor 84 and traction wheel W1.

As best seen in FGS. l, 2 and ll, rotor 3S is provided with a plurality of spaced radial slots SiS-313, in which are slidably retained a series of vanes .3M-32th Vanes 3203Z0 are pressed outwardly by means of springs 322-322 into sliding Contact with the interior of above mentioned stator 9i), it being understood that'rotor 38 lits against a complementary surface 324 of axle housing 390 and against a surface 326 of dividing unit 362 in a substantially fluid-tight manner as also do vanes 32h-32). Vanes 3520-32@ also lit in slots 313 in a fluid-tight manner while all of these several parts are at the same time freely movable in relation to each other. Stator 93 has an internal cam-like surface 228 against which vanes 32%- 320 are pressed by springs 322 so as to slide thereon as rotor 3S rotates. Cam surface 223 alternately approaches and recedes from rotor 33 so that vanes S20-320 are alternately pressed into and extended from slots 323. As will be apparent, this arrangement results in a series of chambers between the consecutive vanes and the rotor and stator and surfaces 324 and 326 respectively which alternately expand and contract as the rotor rotates. Pressure fluid is introduced into the expanding chambers and exhausted from the contracting chambers, resulting in an unbalanced pressure on the vanes which causes rotation of the rotor.

As seen best in FIGS. l, l and 11, passageway 32 communicates with a port 33@ in the face of unit 302 which communicates with the spaces between vanes 326- 32! where they are expanding during forward rotation. A passageway 332 forming a continuation of passageway 82 communicates with a port 334 also communicating with the spaces between vanes 32S where they are expanding during forward rotation of the parts. An exhaust port 336 communicates in similar manner with said spaces in the region where they are being contracted 'oy the rotation of rotor 88 and connects by means of a passageway 33S (see also FIG. l2) with a port 340 communicating with another series of contracting spaces between vanes 329. Passageway 333 has a branch 342, FiG. l, communicating with a fitting 34d which connects with a branch pipe 346 leading into above mentioned port 178 so as to deliver part of the spent fluid to the spaces between vanes 176 of pump rotor 66. Fitting 344 also cornmunicates with a branch pipe 343 leading into above mentioned port 19u so as to deliver the rest of the spent iiuid to the spaces between the vanes of pump rotor 64. It will now be apparent that the fluid is trapped in a closed circuit, or plurality of circuits, and travels back and forth between pump 52 and motor 6d so as to actuate the latter when power or energy is put into the former.

Motor stator 90, as 343 hereinbefore indicated has an internal cam shape, a surface 343 being formed preferably on a true radius about the center of shaft 31.0 corresponding substantially with that of rotor 83. Stator 90 also has a surface portion 35@ and 352 formed preferably on a true radius about shaft 3ft), larger than the radius about which surface portion 3433 is formed. Between surface portions 34S and 352 is a transitional or easement surface portion 354 merging with both surface portions 348 and 352. It will now be apparent that vanes 3253, while traveling on surface portion 343 will not move relatively to rotor S8. Similarly, when traveling on surface portion 352 vanes 323 will remain stationary in relation to rotor 88. It will be further noted that, while vanes 32? are traveling on surface portion 354 so as to be forced ia inwardly relatively to rotor 83, exhaust port 349 is in communication with both sides of each vane so that there can be no differential of pressure on the two sides of any vane while it is sliding into its slot in rotor SS. The same is true of pressure port 334, which communicates with the space on both sides of each of vanes 320 when the latter are traveling on a surface portion 33d merging between above mentioned surface portion 352 and a surface portion 353. Thus although the pressure is comparatively high at this point it is equalized on the two sides of the vanes so they are not strained and cramped in the slots when moving out on surface portion 356. The pressure differential which does the driving is exerted on the vanes in contact with surface portion 352, which, as above stated, is formed on a true radius about shaft 310, the vanes being fully extended and receiving the full pressure on the side of port 334 and the exhaust pressure on the side of port 343. As heretofore stated vanes 320 do not move in slots 3l@ while traveling on surface portion 352, and this is the only region in which substantial circumferential thrust is exerted on the vanes. Since the vanes do not slide in the slots when under this thrust, there is no substantial wear, and the motor will have a satisfactory service life. A companion surface portion 360 is provided preferably diametrically opposite surface portion 352 between transitional surface portions 362 and 364 and which works with vanes 320 between ports 33t) and 33d in a similar manner.

The provision of duplicate pressure ports, exhaust ports, surfaces 352 and 36@ results in a substantially perfectly balanced rotor, and eliminates many of the difficulties heretofore experienced with vane type positive displacement motors in the past. The pressure entering through pressure port 334, as well as tending to rotate rotor 88, tends to push it backwardly and downwardly with a very substantial force, but a substantially identical force is developed by the pressure fluid entering through pressure port 334, tending to force rotor 88 in a forward and upward direction. Furthermore, the turning effort exerted on the vanes which are forwardly disposed at any instant, and which is exerted in a downward direction, is matched by a substantially equal upward force onthe vanes which happen to be at the rear and receiving pressure fluid from port 33d. Thus the resultant force on rotor 8S, insofar as the hydraulic pressure is concerned is substantially pure tortion, there being no detrimental side thrust or extraneous load on bearings 312 and 31S caused by the action of motor 6?.

Vanes 32@ may beV of a variety of constructions within the contemplation of the invention, but may advantageously be made of a portion 3&6, FlGS. 31, 32 and 33, having a notched end 363 complimentary to a notched end 379 of a portion 3?2, ends 36S and 370 being recessed as at 374 to receive springs 3% which tend to expand the vanes laterally as seen in FIG. 32 so as to lit surfaces 324 and 326, FIG. 11. Portion 36d has a recess 3'7'7 and portion 372 has a recess 373 for reception of above mentioned springs 322 in the same manner as vanes 323, and which serve to keep the vanes extended radially against the several surface portions of stator el).

Since the whole structure operates substantially full of duid it is necessary to vent the spaces within slots 318, since otherwise fluid therein would prevent movement of vanes 320. For this purpose a groove 33@ is formed about one or both faces of rotor S8 communicating with all of grooves 318, and, since the movements of the vanes in and out are preferably symmetrical and complimentary, there is always fluid ready to follow an extending vane, and always a place for lluid in any slot 313 to go. This is accomplished without venting these spaces to exhaust pressure, which might cause undesired retracting of the vanes, or directly connecting them with high pressure, which might cause short circuiting ofthe pressure liuid through the slots. A pressure equalizing groove 382 is formed on the face of rotor S8 in contact with surface Vequa'lizing passageway 388, FIG. 1, extends from the space vabove to the space below'valvebody 242, a drain passage- `Way 390 leading from the `lower space into housing H.

Thus any seepage axially of the valve is drained away and does not develop any pressure tending to either raise or Vlower Vvalve body 242.

-Ventng'and fluid replenishment 4'Unavoidable slight leakage from pump .unit S2 and 'from motor unit 60 also accumulates in housing H and is automatically returned tothe circuit. As seen particularly `in-FIGS. 18, 19 and 20, an auxiliary pump generally desig- -nated as 392 picks up the accumulated-fluid from housing H and forces it'into one or the other of pipes 54 and 56 or into fitting 344, as Will appear. A suction vchamber 394 lspaced above the bottom of housing H'has a filtering portion 396 through which uid may ilow to a suction tube 398 leading into pump body 40G in which are rotatable, intermeshed impeller rotors or gears 402-and 404.

VRotor-404 is lixed on a shaft 406 which is driven at all times when pump unit`52 is -in operation by means of a sprocket 40S actuated by a chain 410 in turn driven by a sprocket 412 forming in thefpresent instance part of above mentioned gear 154. Pump body 40) may be lsupported -in any suitable manner, but in the present yinstance is carried on a stud 414 engaged with a side of housing H by ymeans of -lock nuts 416-416. Rotors 402 and 404 `transfer uid from a suction chamber 41S to a discharge chamber 420 with the development of substantial pressure inthe latter, and stud 414 is contemplated as `being made hollow and connected to a tube 422 through which iiuid may pass toany desired auxiliary fluid operated device, `Within the capacity of pump 392, such for example as a hydraulic power lift, -servo mechanism or the like. Chamber 420 has a by-pass generally designated as 424 comprising a body portion 426 in the present instance constituting a cover for pump body 409, and providing a passageway 428 leading out of chamber 420 and communicating with a shouldered bore 430 in which is slidably received a plunger 432 pressed in one direction by-a spring l434 retained by a closure 436. When the desired pressure'has been attained in chamber 421),'plunger 432 'is ,pressed downwardly, compressing spring 434 until the upper end of plunger 432 uncovers a port 43S communicating with suction chamber 418. Fluid then passes through by-pass 424 from discharge chamber 421Mo suction chamber 4iS, and the pressure in chamber 420 is 'prevented from rising to an undesirable value, but remains available at all times when pump unit 52 is running.

Chamber 420has a plurality oi' outlets 449, 442 and 444, closed by non-return valve elements 446, 44S and 450rrespectively. Outlet 442 communicates, through a it- 4ting'452, FIG. 2O and pipe 454, FIG. 18 with above nientioned fitting 344, while outlet 440, in similar manner communicates through a pipe 456 with above mentioned pipe '56. Also similiarly, outlet 444 communicates througha pipe 458 with above mentioned pipe S4. As willnow be apparent, since in operation spent huid will be returning to pumping unit 52 through ttings 344 or pipes 54 and 56, either the latter or tting 344 will be carrying substantially zero pressure, and the pressure maintained Yin 'chamber 420 will be suiicient to displace one oranother of valve elements 446, 448 or 450 so as to insure that -whicheverconduits are carrying spent fluid will be kept completely full at all times, and infact-under a slight positivepressure. As will be apparent, fluid under working pressure in pipes Y54 and 56, or in fitting 344 during reverse operation, cannot` get into chamber 420, since it is prevented by, and will serve only to more rmly i4 `seat Whichever of valves 44e, 44S or 45t) is or are exposed to it.

In this way the iiuid circuitiis keptentirely full in spite of slight seepage, and negative pressures A(below atmospheric) which would tend'to cause iniiltration of air into 'the low pressure passageways, are avoided.

FIGS. 25 to 28 inclusive show a modification, the scale being somewhat reduced, which Will-havecertain adv-antages under certain conditions of use such for example as cultivating. In this arrangement la pumping unit generally designated as 460, which may be identical with above described pumping unit 52, is driven from la tractor engine not shown, by means of a drive shaft y462, and imp-els fluid through :a selector valve A464 yfrom which it is Idistributed to a pair ofiiui-d motors genenally designated as 466 tand 46?, which are :substantially identical, except lfor size, with motore() hereinbefore described, and being supplied with stators 476 .and 472 within which operate rotors 474 and 476 respectively (in .a manner identical with that previously described). In this modiiication, however, rotor 474 is lmounted on a drive shaft 473-car ried in bearings 48) and 482 and driving, through a gear 484 .a gear 48o on :a stub Aaxle 43S carried in bearings 500 and 542, the mechanism being carried in housings S64 and '5% providing a drop axle 'effect especially useful in cultivating tall crops-which would be damaged by the center` portion of common types of low rear axles. It wil-l be understood that motor 463 is provided with la sub-stantially identi-cal drive-shaft, gears and axle, and which-have therefore been given 'thee-same numbers as the corresponding parts associated with motor 466. y

While the last described arrangement does not avoid :all gearingin the drive train, as does the previously described embodiment, it does eliminate all but the final `drive gears which arevquite rugged and tnouble-free. It will be noted that motors 466 and 46S are arranged torotate in directions 'opposite to their respective axles, and that they make 'several revolutions to one of their respective axles, the

more rapid rotation tending to reduce the proportion of slipncaused by unavoidable V'slight leakage through the motors. It will be understood that axles 488 have drive for traction wheels, and that the :other essential parts of the tractor are of any suitable or well-known form.

'Since the iiuid in the `fluid circuit will be continuously agitated, it is contemplated to Iinclude la cooling device in the circuit to dissipate any excessive amount of head which may be generated.

As seen in PEG. l, a seat 5% is carried on the tractor by means of a-shock absorbing device 'of suitable type Vgenerally designated as 'Siti and which places an operator in a suitable position to lactuate contuol bar 252 and a hinged detent 512 is provided on fitting 25) and which engages abutments 514 and 516 :as valve 53 is turned by means of bar 252 into positions corresponding respectively ,approximately with FIGS. 22 and 23, yfor directing all the power to the left, or t-o the right traction units, 'as the case may be. If it is desired to obtain the non-dilierential or solid axle effect, detent '512 is rocked on its hinge and may enter :a notch 5-18'in abutment 516 and permit .addition-al movement of bar 252, placing valve -53 in the position indicated :in FIG. 24.

The operation of the tractor and the various novel `and advantageous lfeatures thereof .are thought to -be clear from the foregoing description, suiiicient to say that the pumps and motors `being of the positive displacement type, a nearly positive drive is established `betvveenthe tractor engine and thetraction-units so-that any serious slip for lossofV eiciency is avoided. A braking leffect is available by placing the pump unit in neutral, whereupon it can transmit substantially no iiuid, while the motors, serving equally well .as positive displacement pumps, cannot rotate if the iiuid is prevented from -cii'culating-'as when it is blocked by the purnps. Control of the pumps aiiords -a virtually continuous variation in ratio between ia minimum or zero speed and -a maximum, and incidentally pro- 'l5 vides a constant running power take-olifr and beltpulley, and the novel selector valve gives the effect of individual wheel brakes and .clutches 'and in addition a solid .axle effect, and furthermore the arrangement provides a supply of fluid under pressure for lauxiliary purposes.

The above being a complete description of kan illustrative embodiment of the invention, what is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a tractor the combination of an engine, a main clutch, a connection driven by the engine and in driving relation to the main clutch, a belt pulley, mechanism including a shaft connected to said main clutch and to said belt pulley so that the belt pulley is driven from the engine through the main clutch, a transmission including a variable displacement fluid pump connected with said shaft so as to be driven from the engine through the main clutch, a fluid motor, conduits connecting the pump and motor, .a traction unit, mechanism connected to said motor and said traction unit, driven by the fluid motor` and driving said traction unit, and said variable pump being iadjustable at will from zero to maximum displacement for operating said motor :at `any speed within the range of adjustment of said pump, `and means for so adjusting said pump while said clutch -is engaged whereby the travel of said tractor may be controlled throughout the speed range afforded by said pump without affecting the operation of said belt pulley.

2. In fa tractor the combination of an engine, a main clutch, a connection driven by the engine land in driving relation to the main clutch, ra power take-olf, mechanism including :a shaft connected to said main clutch and to said power take-olf so that said power take-off is driven from the engine through said main clutch, a transmission driven from the engine through said main clutch including a variable displacement pump connected with said shaft so las to be driven by said clutch, a -uid motor, conduits connecting the pump land motor for actuating the motor in response to driving of the pump by the engine, a traction unit mechanism connected in driven relation to the fluid motor and in driving relation to said tractor unit, said pump having a part which is adjustable for altering the displacement of said pump, said part being adjustable at will from zero to maximum displacement for `operating said motor -at `any speed from stand-still to maximum, and means for so adjusting said part while said main clutch is engaged and said engine is running, whereby said tractor may be controlled throughout the entire speed range :afforded by said pump without affecting the operation of said power take-off.

3. In a tnactor the combination lof an engine, la main clutch, a connection driven by the engine and in drive relation to the main clutch, a belt pulley mechanism including a shaft connected to the main clutch and to said Ibelt pulley so that the belt pulley is -driven from the engine through the main clutch, -a transmission including a fluid pump connected with said shaft so as to be driven lfrom the engine through the main clutch, a duid motor, conduits connecting the pump and motor, a traction unit mechanism connected to said motor and said tnaction unit, driven by the fluid motor :and driving said traction unit land said transmission being adjustable at will from zero to maximum displacement for operating said motor at any speed within the range of adjustment, -of said transmission, said transmission including a shiftable part which is adjustable for .altering the displacement of said transmission While said clutch is engaged, 'adjustment of said part providing a range of speeds and ratios in one direction equivalent to those `available in the other direction, ,and means for adjusting said shiftable part whereby the travel of said tractor may be completely controlled without affecting the operation of said belt pulley.

4. In a tractor the combination of ian engine, a main l clutch driven by the engine, la power take-off driven from the envinc throu h said main clutch, a transmission driven from the engine through said main clutch including a duid pump connected to be driven by said clutch, a fluid motor, conduits connecting the pump land motor for actuating the motor in response to driving of the pump by the engine, and a traction -unit connected in driven relation to the fluid motor, said transmission including a part which is adjustable at will for altering the displacement lfrom zero to maximum for operating said mot-or at any speed from standstill to maximum in either 4direction while said clutch is engaged and said engine is running, and means for adjusting said adjustable part whereby said tir-actor may be controlled throughout its entire speed range without affecting the operation of said power take-off.

5. In a tractor the combination of an engine, a main clutch driven by the engine, a belt pulley driven from the engine through the main clutch, a transmission including a variable displacement -uid pump driven from the engine through the main clutch including a part which is shiftable for 'altering the displacement thereof, a reversible fluid mot-or, conduits connecting the pump and motor to provide -a substantially closed uid circuit, a traction unit driven by the fluid motor, and said variable pump being ladjustable lat will from zero to maximum displacement in either direction for operating said motor .at any speed within the range of adjustment of said pump in either direction While said clutch is engaged, and means for adjusting said shiftable part whereby the travel of said tractor may be completely controlled without affecting the operation of said belt pulley.

6. In a tractor the combination of an engine, a main clutch driven by the engine, a power take-off driven from the engine through said main clutch, a transmission driven from the engine through said main clutch including a variable displacement pump connected to be driven by said clutch including a part which is shiftable for altering the displacement thereof, a reversible fluid motor, conduits connecting the pump and motor to provi-de a substantially closed fluid circuit for actuating the motor in response to driving of the pump by the engine, and a traction runit connected in driven relation to the fluid motor, said pump being adjust-able .at will from zero to maximum displacement in either direction for operating said motor at any yspeed from stand-still to maximum while said clutch is engaged and said engine is running, and means for adjusting said shiftable part whereby said tractor may be completely cont-polled throughout its entire speed range without alfecting the ope-ration of said power take-off.'

7. In a tractor the combination of an engine, -a belt pulley, motion transmitting means connected with the engine 4and with the belt pulley for driving the belt pulley from the engine, a transmission including a -uid pump driven from the motion transmitting means, a `fluid motor, conduits connecting the pump and motor, a traction unit driven by the duid motor, land clutch means connected with the motion transmitting means, said clutch means being ialso connected with said pump, said clutch means being shiftable for disconnecting said pump from said mot-ion transmitting means t-o provide for use of said belt pulley without operating said pump at times when said pump is not needed.

8. In a tractor the combination of an engine, a shaft extending longitudinally from said engine, .a duid pump having a pump shaft extending therethrough driven -Jnrom said engine shaft, a transmission including said pump, a fluid motor, conduits connecting the pump and the motor for actuating the motor in response to driving of the pump by the engine, .a traction unit connected in driven relation to the fluid motor and 1a power take-off shaft extending fr-om said pump on the side thereof remote from said engine, driven by said pump shaft and operable by rotation of said pump shaft.

9. In a tractor the combination of an engine, a main clutch driven by .the engine, a rearwardly extending power take-off shaft driven from the engine through said main clutch, means for disconnecting said power take-olf shaft for discontinuing its operation independently 'of Isaid main clutch, a transmission driven from the engine through said main clutch including a variable displacement pump loonnected to be driven lby said `clutch ,and including a part which is shiftable for valtering the displacement of said pump, ra fluid motor, lconduits connecting the pump `and motor for actuating the mot-or in response to driving of the pump by the engine, land a traction unit lconnected in driven relation to the uid motor, said pump being adjustable at will from zero to maximum displaeement for operating -said motos- `at any speed from lstandstill to maximum While -said clutch Vi-s engaged yand said engine i-s running, and means for shifting said shiftaole part whereby said tractor may be controlled throughout its entire speed range without aecting the operation .of said power takeolf.

References Cited by the Examiner UNITED STATES PATENTS Noron 180-66 X Johnston et Ial 180-5'3 X Strehlow 180-53 X Stumpf ISO-53 X Hamren 180-6.48 Tucken 103-120 Ferris 103-1 20 Kopp 180-66 Long 180-53 Swenson et al 180-53 5 A. HARRY LEVY, Primary Examiner.

PHILP ARNOLD, Examiner. 

1. IN A TRACTOR THE COMBINATION OF AN ENGINE, A MAIN CLUTCH, A CONNECTION DRIVEN BY THE ENGINE AND IN DRIVING RELATION TO THE MAIN CLUTCH, A BELT PULLEY, MECHANISM INCLUDING A SHAFT CONNECTED TO SAID MAIN CLUTCH AND TO SAID BELT PULLEY SO THAT BELT PULLEY IS DRIVEN FROM THE ENGINE THROUGH THE MAIN CLUTCH, A TRANSMISSION INCLUDING A VARIABLE DISPLACEMENT FLUID PUMP CONNECTED WITH SAID SHAFT SO AS TO BE DRIVEN FROM THE ENGINE THROUGH THE MAIN CLUTCH, A FLUID MOTOR, CONDUITS CONNECTING THE PUMP AND MOTOR, A TRACTION UNIT, MECHANISM CONNECTED TO SAID MOTOR AND SAID TRACTION UNIT, DRIVEN BY THE FLUID MOTOR AND DRIVING SAID TRACTION UNIT, DRIVEN BY THE FLUID MOTOR BEING ADJUSTABLE AT WILL FROM ZERO TO MAXIMUM DISPLACEMENT FOR OPERATING SAID MOTOR AT ANY SPEED WITHIN THE RANGE OF ADJUSTMENT OF SAID PUMP, AND MEANS FOR SO ADJUSTING SAID PUMP WHILE SAID CLUTCH IS ENGAGED WHEREBY THE TRAVEL OF SAID TRACTOR MAY BE CONTROLLED THROUGHOUT THE SPEED RANGE AFFORDED BY SAID PUMP WITHOUT AFFECTING THE OPERATION OF SAID BELT PULLEY. 